Process and apparatus with refractory shelf for hydrodynamic mixing zone

ABSTRACT

A shelf is incorporated into a typical FCC riser that permits the tips of the nozzles to extend past the wall of the riser while preventing the tips from promoting coke build-up and protecting the tips from erosion. The shelf can be part of an angled section that often appears in a transition zone for increasing the internal diameter of the riser to accommodate the volumetric expansion of the feed. The shelf section reduces the non-uniformity in the mixing of the catalyst and feed and minimizes backmixing of the feed injection. The shelf of this invention accomplishes these objectives without recessing the feed injectors into the riser wall which can interfere with the spray pattern. The shelf provides a location for the tips of the upwardly directed feed injectors which virtually eliminates quiescent areas that were the sites for riser coking and that resulted from the protrusion of nozzles and/or nozzle protection devices into the riser. The uninterrupted flow path about the nozzles can replenish catalyst and erode away coke if it does form downstream of the reaction zone. This invention is particularly suited for small diameter risers where nozzle projection has the most disrupting influence on the catalyst and oil flow through the riser. This invention may also be used in conjunction with a contoured riser cross-section that shapes the interior of the riser downstream of the nozzles into a polygonal cross-section that matches the spray pattern of the nozzles.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to the dispersing of liquids intofluidized solids. More specifically this invention relates to a methodand apparatus for dispersing a hydrocarbon feed into a stream offluidized particles.

2. Description of the Prior Art

There are a number of continuous cyclical processes employing fluidizedsolid techniques in which carbonaceous materials are deposited on thesolids in the reaction zone and the solids are conveyed during thecourse of the cycle to another zone where carbon deposits are at leastpartially removed by combustion in an oxygen-containing medium. Thesolids from the latter zone are subsequently withdrawn and reintroducedin whole or in part to the reaction zone.

One of the more important processes of this nature is the fluidcatalytic cracking (FCC) process for the conversion of relativelyhigh-boiling hydrocarbons to lighter hydrocarbons boiling in the heatingoil or gasoline (or lighter) range. The hydrocarbon feed is contacted inone or more reaction zones with the particulate cracking catalystmaintained in a fluidized state under conditions suitable for theconversion of hydrocarbons.

It has been found that the method of contacting the feedstock with thecatalyst can dramatically affect the performance of the reaction zone.Modern FCC units use a pipe reactor in the form of a large, usuallyvertical, riser in which a gaseous medium upwardly transports thecatalyst in a fluidized state. Ideally the feed as it enters the riseris instantaneously dispersed throughout a stream of catalyst that ismoving up the riser. A complete and instantaneous dispersal of feedacross the entire cross section of the riser is not possible, but goodresults have been obtained by injecting a highly atomized feed into apre-accelerated stream of catalyst particles. However, the dispersing ofthe feed throughout the catalyst particles takes some time, so thatthere is some non-uniform contact between the feed and catalyst aspreviously described. Non-uniform contacting of the feed and thecatalyst exposes portions of the feed to the catalyst for longer periodsof time which can in turn produce overcracking and reduce the quality ofreaction products.

It has been a long recognized objective in the FCC process to maximizethe dispersal of the hydrocarbon feed into the particulate catalystsuspension. Dividing the feed into small droplets improves dispersion ofthe feed by increasing the interaction between the liquid and solids.Preferably, the droplet sizes become small enough to permit vaporizationof the liquid before it contacts the solids. It is well known thatagitation or shearing can atomize a liquid hydrocarbon feed into finedroplets which are then directed at the fluidized solid particles. Avariety of methods are known for shearing such liquid streams into finedroplets.

Another useful feature for dispersing feed in FCC units is the use of alift gas to pre-accelerate the catalyst particles before contact withthe feed. Catalyst particles first enter the riser with zero velocity inthe ultimate direction of catalyst flow through the riser. Initiating orchanging the direction of particle flow creates turbulent conditions atthe bottom of the riser. When feed is introduced into the bottom of theriser the turbulence can cause mal-distribution and variations in thecontact time between the catalyst and the feed. In order to obtain amore uniform dispersion, the catalyst particles are first contacted witha lift gas to initiate upward movement of the catalyst. The lift gascreates a catalyst pre-acceleration zone that moves the catalyst alongthe riser before it contacts the feed. After the catalyst is moving upthe riser it is contacted with the feed by injecting the feed into adownstream section of the riser. Injecting the feed into a flowingstream of catalyst avoids the turbulence and back mixing of particlesand feed that occurs when the feed contacts the catalyst in the bottomof the riser. A good example of the use of lift gas in an FCC riser canbe found in U.S. Pat. No. 4,479,870 issued to Hammershaimb and Lomas.

There are additional references which show the use of a lift gas innon-catalytic systems. For example, in U.S. Pat. No. 4,427,538 toBartholic, a gas which may be a light hydrocarbon is mixed with an inertsolid at the bottom part of a vertical confined conduit and a heavypetroleum fraction is introduced at a point downstream so as to vary theresidence time of the petroleum fraction in the conduit. Similarly, inU.S. Pat. No. 4,427,539 to Busch et al., a C₄ minus gas is used toaccompany particles of little activity up a riser upstream of chargedresidual oil so as to aid in dispersing the oil

U.S. Pat. Nos. 5,554,341; 5,173,175; 4,832,825 and 3,654,140 all showsthe use of radially directed feed injection nozzles to introduce feedinto an FCC riser. The nozzles are arranged in a circumferential bandabout the riser and inject feed toward the center of the riser. Thenozzle arrangement and geometry of the riser maintain a substantiallyopen riser cross-section over the feed injection area and downstreamriser sections. The angled feed nozzles are typical of those used toinject feed or other fluids at an intermediate portion in the riserconduit. The angled feed injectors present a number of problems for theoperation of the risers. The nozzles typically extend away from the wallof the riser and into the flow path of the catalyst. Passing particlesover the nozzles at high velocity can result in erosion. The nozzleprotrusion can also result in quiescent zones that promote backmixingand provide sites for coke build-up to begin. The protrusion of the feedinjectors can provide such zones by protecting coke from the naturalerosion action of the flowing catalyst which would otherwise eliminatethe coke from these sites. Excessive coke buildup can upset thehydraulic balance in a unit to the point where it is eventually forcedto shut down. The processing of heavier feeds such as residualhydrocarbons can exacerbate coke production problem due to their highercoking tendencies.

An obvious solution to the problem of nozzle protrusion would be torecess the nozzles completely into the wall of the riser and therebyremove them from the catalyst flow path. This solution is notsatisfactory since the feed injector tips are specifically designed toprovide a relatively uniform coverage of the hydrocarbon feed over thecross-section of the riser by expanding the pattern of feed injection asit exits from the nozzle. Completely recessing the tips of the injectornozzles within the wall of the riser disrupts the ability to obtain aspray pattern over the majority of the riser cross-sectional area

It is an object of this invention to more uniformly distribute catalystand oil over the cross-section of the riser.

It is another object of the invention to reduce areas of local variationin particle density to improve oil penetration into the particles.

It is a further object of the invention to minimize areas of backmixingand quiescence around the feed injectors that can lead to cokeformation.

BRIEF SUMMARY OF THE INVENTION

These objects are achieved by providing a hydrodynamic mixing zone wherea plurality of feed injectors circle an intermediate portion of acontacting conduit to inject a feed into a flowing stream of particulatematerial. The hydrodynamic zone is also referred to as the injectorzone. The invention locates the outlets of the feed injector nozzles ina shelf from which the tips of the nozzles protrude. The shelf is formedby an abrupt change in the diameter of the conduit relative to theadjacent upstream portion of the conduit. This divergence in thediameter of the conduit locates the protruding tips of the feedinjectors outside of the direct flow path of the passing particulatematerial and maintains active and flowing particles in the regionsimmediately upstream and downstream of the injector tips. The shelfthereby improves the hydrodynamics in the contacting zone by eliminatingthe deleterious effects of the previous protrusion of the nozzles intothe particle flow without recessing the nozzles into the wall of thecontacting conduit. The invention thereby reduces any non-uniformity inthe mixing of the particles and feed and by eliminating sites with ahigh potential for backmixing of the feed with the particles.

The shelf can be part of a normal transition zone that increases thesize of the riser to provide a larger riser cross-sectional area. Thelarger cross sectional area is usually necessary to accommodate avolumetric expansion of the feed. This expansion of the feed issometimes referred to as a molar expansion. The injectors normallydirect the incoming feed at a downstream angle with respect to theparticle flow. Tapering the shelf so that it provides an angled surfacebetween the smaller upstream diameter and larger downstream diameter ofthe riser further reduces any quiescent area for backmixing or cokeinitiation. Locating the tips of the upstream directed feed injectorsabout the angled shelf section virtually eliminates the quiescent areasthat were sites for riser coking. This uninterrupted flow pathreplenishes particles and erodes away coke in the dense form downstreamof the initial feed injection point. This invention is particularlysuited for small diameter contacting conduits where the nozzleprojection can have the most disrupting influence on the particle andfeed flow through the conduit.

This invention can further reduce quiescent areas by contouring profileof the contacting conduit in the location of feed injection to moreactively suite the specific spray pattern of the injectors. Theinjectors will often create a planar spray pattern that extendshorizontally over the contacting conduit in a fan shaped pattern. Thefan-shaped spray stream from several injectors will collide as they meeteach other to form a polygon. Where the outer edges of each injectionnozzle spray pattern project in a line to the adjacent injector, thepolygon pattern will have a number of sides equal to the number ofinjectors. Areas outside the polygon pattern, but inside the typicallycircular cross-section of the contacting conduit can account for 10-20%,or more, of the conduit area that is not fully utilized for contacting.In accordance with this invention, the areas to the outside of the spraypattern, but within the circular cross-section of the contacting conduitmay be blocked or filled in to eliminate potentially quiescent areasbetween the injector nozzles. Molding of a castable or pneumaticallyapplied refractory lining to the specific contour of the spray nozzlescan provide a satisfactory filler material.

Whether used with or without a contoured lining, the overall width ofthe injector zone is kept relatively narrow. The width of this zone willusually not exceed twice the diameter of the nozzle that provides theinjector tip and, more typically, will have a total width thatapproximates the nozzle size.

Accordingly, within a method embodiment, this invention includes themixing of fluidized particles with a fluid feed stream comprised ofhydrocarbons to produce a dense bed of fluidized particles. To producethe dense bed of fluidized particles, the fluidized particles and afluidizing medium are combined in an upstream section of a contactingconduit. The dense bed of fluidized particles passes downstream in thecontacting conduit through an injector zone that is defined by acircumferential band of the conduit that diverges the diameter of theconduit relative to the adjacent upstream portion and that positions aplurality of discrete feed injection outlets at the wall. At least aportion of a nozzle that provides the feed injection outlet protrudesfrom the wall of the conduit and injects feed at an angle relative tothe conduit axis into a downstream section. The protrusion of the nozzlefrom the wall of the conduit does not extend into an axial projection ofthe inner conduit wall that extends downstream from the starting pointof the diverging conduit diameter. The dense bed of fluidized particlesis passed downstream from the injector zone to the downstream section ofthe conduit that provides a less divergent diameter interior immediatelydownstream of the injector zone. The feed and particles are thencontacted downstream of the feed injection outlets to produce a mixtureof contacted feed and particles. The mixture of contacted feed andparticles is then passed to a separation zone for separation of thecontacted feed from the contacted particles.

In an apparatus embodiment, this invention is a contacting conduit forcontacting catalyst with an at least partially liquid phase fluid.Preferably the contacting conduit is vertically oriented. The contactingconduit is elongated and has both an upstream and a downstream end. Theupstream end of the contacting conduit defines a particle inlet foradding particles and a fluidizing inlet to inject a fluidizing mediumand to produce a dense particle bed. Between the upstream and downstreamends of the contacting conduit is a narrow band that defines adiscontinuous increase in the inside diameter of the conduit from theupstream to the downstream ends of the conduit and thus divides theconduit into upstream and downstream sections. Circling the conduit andfixed with respect to the band, a plurality of feed injectors defineoutlet nozzles that extend from the inside wall of the riser and remainoutside the projection of a surface projected along the axis of theconduit from the inner circumference of the upstream conduit at itsjunction with the band. And at the other end of the vertical contactingconduit is the downstream end that defines a fluid outlet.

Additional objects, embodiments and details of this invention can beobtained from the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional elevation of an FCC reactor and riser.

FIG. 2 is an enlarged section showing a mid portion of the riser of FIG.1.

FIG. 3 is a modified section of the riser section of FIG. 2.

FIG. 4 is a plan view of a nozzle arrangement.

FIG. 5 is a modified plan view of the nozzle arrangement of FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

This invention will be described in the context of an FCC process forthe catalytic cracking of hydrocarbons by contact with a fluidizedcatalyst. The invention may be used in any process that requires adispersion of a fluid into a fluidized particle stream as it passesthrough a conduit.

In a typical FCC process flow arrangement, finely divided regeneratedcatalyst leaves a regeneration zone and contacts a feedstock in a lowerportion of a reactor riser zone. FIG. 1 shows a reactor 10 with avertical riser 20 having an upper section 12 and a lower riser portion14 into which a regenerator standpipe 16 transfers catalyst from aregenerator (not shown) at a rate regulated by a slide valve 11. Afluidization medium enters the riser through a nozzle 17 and a suitabledistribution device (not shown). The fluidizing medium may be a diluentmaterial, typically steam, or a hydrocarbon stream that undergoes someconversion or passivates the catalyst. The fluidized catalyst flowsupwardly through lower riser portion 14 at a relatively high densityuntil it reaches a plurality of feed injection nozzles 15 (only one isshown) that inject a hydrocarbon feed across the flowing stream ofcatalyst particles. Upper riser section 12 has a larger internaldiameter than lower section 14 to accommodate the volumetric expansionof the feed as it expands through contact with the hot catalyst. Whilethe resulting mixture, which has a temperature of from about 200° C. toabout 700° C., passes up through the remainder of the riser, conversionof the feed to lighter products occurs and coke is deposited on thecatalyst. The effluent from the riser is discharged from the top 19 ofriser 20 through a disengaging arm 21 that tangentially discharge themixture of catalyst and gases into a disengaging chamber 23 to effect aseparation of the gases from the catalyst. A transport conduit 22carries the hydrocarbon vapors and entrained catalyst to one or morecyclone separators 24 that separate any spent catalyst from thehydrocarbon vapor stream.

A collection chamber 25 gathers the separated hydrocarbon vapor streamsfrom the cyclone for passage from an outlet nozzle 28 into afractionation zone (not shown) known in the art as the main column. Themain column separates the hydrocarbon vapors into such typical fractionsas light gases and gasoline, light cycle oil, heavy cycle oil and slurryoil. Various fractions from the main column can be recycled along withthe feedstock to the reactor riser. Typically, fractions such as lightgases and gasoline are further separated and processed in a gasconcentration process located downstream of the main column. Some of thefractions from the main column, as well as those recovered from the gasconcentration process may be recovered as final product streams.

The separated spent catalyst from cyclones 24 passes through dip legs 30into the lower portion of collection space 31 and eventually passes intoa stripping zone 32 across ports (not shown) defined by the bottom ofdisengaging chamber 23. Catalyst separated in disengaging chamber 23passes directly into stripping zone 32. A stripping gas, usually steam,enters a lower portion of stripping zone 32 through an inlet 33 and maybe distributed by one or more distributors (not shown). The strippinggas contacts the spent catalyst to purge adsorbed and interstitialhydrocarbons from the catalyst. A series of baffles 35 in the strippingzone improves contact between the catalyst and stripping gas. Additionalgas for fluidization or stripping may be added through one or moreinlets 38.

The spent catalyst containing coke leaves the stripping zone through areactor conduit 36 and passes into the regeneration zone where, in thepresence of fresh regeneration gas and at a temperature of from about620° C. to about 760° C., combustion of coke produces regeneratedcatalyst and flue gas containing carbon monoxide, carbon dioxide, water,nitrogen and perhaps a small quantity of oxygen. Usually, the freshregeneration gas is air, but it could be air enriched or deficient inoxygen. Flue gas is separated from entrained regenerated catalyst bycyclone separation means located within the regeneration zone andseparated flue gas is passed from the regeneration zone, typically, to acarbon monoxide boiler where the chemical heat of carbon monoxide isrecovered by combustion as a fuel for the production of steam, or, ifcarbon monoxide combustion in the regeneration zone is complete, theflue gas passes directly to sensible heat recovery means and from thereto a refinery stack. Regenerated catalyst which was separated from theflue gas is returned to the lower portion of the regeneration zone whichtypically is maintained at a higher catalyst density. A stream ofregenerated catalyst leaves the regeneration zone, and in repetition ofthe previously mentioned cycle, contacts the feedstock in the reactionzone.

Catalysts that can be used in this process include those known to theart as fluidized catalytic cracking catalysts. Specifically, the highactivity crystalline aluminosilicate or zeolite-containing catalysts canbe used and are preferred because of their higher resistance to thedeactivating effects of high temperatures, exposure to steam, andexposure to metals contained in the feedstock. Zeolites are the mostcommonly used crystalline aluminosilicates in FCC.

Catalyst entering the lower section 14 of the riser conduit preferablyforms a dense catalyst bed. The term dense bed refers to a region ofcatalyst having a density of at least 20 pounds per cubic foot. Thedense bed zone is also termed a bubbling bed which provides good mixingof the catalyst and a uniform suspension of catalyst as it passes intocontact with feed from injection nozzles 15. The quantity of fluidizinggas entering the bottom of the riser is usually added in an amount thatcreates a low upward velocity of catalyst having a velocity of less than6 feet per second and usually in a range of from 3 to 5 feet per second.This invention does not require a specific gas composition for thefluidizing medium. Steam can serve as a suitable fluidizing medium. Thefluidizing medium can also comprise a typical lift gas and can be usedby itself or in combination with steam. Lift gas typically includes notmore than 10 mol % of C₃ and heavier hydrocarbons. In addition tohydrocarbons, other reaction species may be present in or comprise thefluidizing mediums such as H₂, H₂S, N₂, CO and/or CO₂.

In accordance with typical FCC practice the feed exits injection nozzles15 as a spray in a fan pattern. The nozzles are usually angled to tipthe fan pattern in a downstream direction. The angle of the nozzles willtypically be in a range of from of at least 20° and less than 70° withrespect to a transverse plane passing through the nozzles. Droplet sizewithin the spray and the velocity of the spray determines momentum ofthe feed as travels across the open riser section. It is difficult toincrease the momentum of the feed above a given level since the velocityof the feed injection is inversely proportional to the size of thedroplets in the emanating spray. Higher velocities for the spray tend todirectly increase the momentum of the spray but indirectly decrease themomentum by reducing the size of the exiting droplets. Conversely thereduced momentum that results directly from lower spray velocities isoffset by the typical production of larger droplets. An expanding gas orgaseous component such as steam may be used in conjunction with anothersource of energy in order to break up the liquid. This other source ofenergy can consist of a high pressure drop for the gas and liquidmixture. Supplying additional energy makes up for inadequate mixing sothat a fine and uniform distribution of droplets will still be obtainedonce the feed is injected into the catalyst. It is also known that thepressure drop across an orifice or port can be reduced while stillobtaining a good dispersion of fine liquid droplets by blending andhomogenizing the liquid and any added gas sequentially in stages ofincreased mixing severity. The feed entering the feed injectors willusually have a temperature below its initial boiling point but atemperature above the boiling point of any steam or gaseous hydrocarbonsthat enter the distribution device along with the liquid. A minimumquantity of gaseous material equal to about 0.2 wt.% of the combinedliquid and gaseous-mixture, is often commingled with the liquid enteringthe injectors. The gaseous material may be introduced into the injectorsin any manner.

Following mixing and ejection, contact of the feed with the hot catalystcreates a volumetric expansion from both the vaporization of liquidhydrocarbons and heating of the vapor as well as cracking of thehydrocarbons into lower molecular weight species. FIG. 2 more clearlyshows the configuration of the feed injection nozzles 15 and the innerconfiguration of the riser wall that defines the shelf 40 of thisinvention. Feed enters the back of injection nozzle 15 via a nozzle 37.Diluents, as previously described, can be injected through a nozzle 38and mixed with the feed. A tip 39 of the injector disperses the feed inan extended horizontal fan pattern through an appropriately designedoutlet nozzle.

The inside of the riser undergoes various changes in diameter toaccommodate the shelf and any requirements for changes in the flowingcross-sectional area to provide the desired velocity and flow regime.Catalyst flowing upwardly from lower portion 14 travels through aninternal section 41 of the riser that has a uniform diameter D₁. As thecatalyst passes upwardly into an injection zone defined by the ring offeed injectors 15 an abruptly enlarged section defines the feedinjection zone that contains the circumferentially extended band of feedinjectors 15. The abrupt enlargement is shown as shelf 40 which has afrusto-conical geometry. However, it is not necessary to this inventionthat the shelf 40 have a flat surface. Contoured surfaces thattransition to the upper riser section 12 may also provide an effectivegeometry for shielding the injector tips 39. Where a frusto-conicalsection defines the injector zone as in FIG. 2 its Included angle willusually be in a range of from 40 to 140°. The outlets of the injectorswill usually occupy at least half of the length along the wall of theinjection zone. Thus, the length L₁ along the injector wall will usuallynot exceed twice the nozzle dimension. In this arrangement total lengthL₁ of the shelf 40 along the internal riser wall is taken up by the feedinjector at the points of feed injection. This narrowly definedinjection zone results in an increase in the conduit diameter over theinjection zone that is less than the width of the nozzles defining theinjection outlets. The overall axial length L₂ of the injector zone willtypically not exceed 8 inches.

The portion of the riser immediately upstream of the injector zone neednot have a uniform diameter, but may be diverging of converging asnecessitated by process requirements. An essential requirement of theinvention is that the lower section of the riser define a trajectory asshown along line T for the particles flowing upwardly past injector tip39. This trajectory line T may be defined as the upstream axialprojection of that portion of the riser located below the injector zone.Thus the trajectory line T will represent either a cylindrical surfaceor a diverging frustro-conical section. It is essential to thisinvention that tips 39 of the nozzles not extend past this projectedtrajectory of the particles from the lower riser portion.

The end of the injection zone is defined by a portion of the conduitthat has a more constant diameter over its length than the injectionzone. The upper part of the hydrodynamic injection section that definesthe injector zone 40 ends with another change in the relative slope ofthe riser wall, shown by line 45, such that the downstream portion ofthe riser has at least a less diverging diameter than the diameterincrease across the injector zone 40. Any variation in the diameteroutside of the injector zone will typically not exceed a 1 in 4 slope.Therefore, the length L₃ of a diverging section 42 as shown downstreamof injector zone 40 in FIG. 2 will have sufficient length L₃ to providea mild diameter divergence until it expands to the diameter D₂. As shownby FIG. 3, the diameter of the riser downstream of the injection zonemay be reduced where desired by a converging diameter section 43.

Referring again to FIG. 2, the internal configuration of the contactingconduit may be fully defined by adjusting the thickness of a refractorylining material 44 contained within the conduit. For example, lowersection 44 would typically have a lining thickness A of 4 to 0.5 inches.The lining thickness may be varied as necessary inside the riser withoutcorresponding changes in the outer diameter of the conduit at the samelocations. A swedge section 48 increases the external diameter of theriser to a uniform upper diameter for upper section 12. The internaldiameter D₁ of the riser remains constant over the increase of diameterfrom riser portion 14 to riser section 12. The shelf as well as the moremildly diverging downstream section 42 are defined completely byvariations in the thickness of the refractory lining until the liningthickness is again reduced to a thickness A that matches the thicknessof the lining below swedge section 48.

The injectors and the shelf defined by the refractory lining are shownin plan by FIG. 4. FIG. 4 shows the preferred arrangement wherein theinjection zone includes at least 4 injector outlets. Shelf 40 extendshorizontally between the inner diameter of lower portion 41 and thechange in slope that marks the downstream end of the injector zone aboutline 45. FIG. 4 also shows the extension of tips 39 outwardly over theshelf section 40. The horizontal extent of the fan spray pattern for thefeed injected by each nozzle 39 is represented by dashed lines 46.Except for the area of the spray tips 39 the overlapping spray patternhas a polygonal shape.

The outer projection of the polygon from the overlapping spray patternleaves an area that does not receive a directed flow feed from thenozzle arrangement. FIG. 5 shows the concavity of the riser crosssection at the location of the feed injection nozzles may be filled inthe cross-hashed area 47 to block this region from catalyst flow. Inthis arrangement, the area to the outside of a cord line drawn betweenthe nozzles and to the inside of the circular diameter of the riser atthe location of the spray tips is blocked so that the polygonal shape ofthe spray pattern receives an upwardly directed flow of catalyst thatmatches the geometry of the spray pattern. The concavity of the riserbetween the nozzle tips need not be fully filled and any decrease in theconcavity between the nozzle tips will reduce the area of catalyst thatreceives the reduced concentration of the feed. Reducing the concavityof the conduit between the injection nozzles result in walls that have agreater degree of discontinuity at the nozzle locations relative to thelocations between the nozzles. The blocked portion 47 may be graduallyreduced in the downstream direction of catalyst flow until the riseragain has an overall circular cross-section. This arrangement therebydecreases the concavity of the conduit wall in a direction normal to theconduit access between the adjacent nozzle locations.

What is claimed is:
 1. An apparatus for contacting catalyst with an atleast partially liquid phase fluid in a contacting conduit, saidapparatus comprising: an elongated contacting conduit having an upstreamend and a downstream end; a particle inlet defined at said upstream endof the conduit for adding particles to said upstream end; a fluidizinginlet defined at said upstream end of the conduit to inject fluidizingmedium and produce a dense particle bed; a swedge section defiling anincrease in the outside diameter of the conduit; a band located betweenthe upstream and downstream ends of the conduit defining a discontinuousincrease in the inside diameter of the conduit from the upstream to thedownstream ends of the conduit and dividing the conduit into upstreamand downstream sections, said band being vertically unaligned with saidswedge section; a plurality of feed injector nozzles circling theconduit and fixed with respect to the band to provide feed injector tipsthat extend from an inside wall of the conduit and from the nozzle andall parts of the feed injector nozzles remain outside this projection ofa surface projected along the axis of the conduit from the innercircumference of the upstream conduit section at its junction with theband; and a fluid outlet defined by the downstream end of the conduit.2. The apparatus of claim 1 wherein the band defines interior wallshaving frusto-conical shape.
 3. The apparatus of claim 2 wherein theslope of the frusto-conical shape has an included angle of from 40 to140°.
 4. The apparatus of claim 1 wherein the band defines walls havinga greater degree of increase in the inside diameter of the conduit atnozzle locations relative to locations between the nozzles.
 5. Theapparatus of claim 4 wherein the band has a generally polygonal crosssection.
 6. The apparatus of claim 1 wherein the inner walls of at leastportion of the upstream or downstream conduit sections diverge orconverge at a slope that is less than the average slope along thelongitudinal axis of the band.
 7. The apparatus of claim 1 wherein theband has a longitudinal length that does not exceed 8 inches.
 8. Theapparatus of claim 1 wherein the conduit is vertically oriented and theupstream end is below the downstream end.
 9. An apparatus for contactingcatalyst with an at least partially liquid phase fluid in a contactingconduit, said apparatus comprising: an elongated contacting conduithaving an upstream end and a downstream end; a particle inlet defined atsaid upstream end of the conduit for adding particles to said upstreamend; a fluidizing inlet defined at said upstream end of the conduit toinject fluidizing medium and produce a dense particle bed; a bandlocated between the upstream and downstream ends of the conduit defininga discontinuous increase in the inside diameter of the conduit from theupstream to the downstream ends of the conduit and dividing the conduitinto upstream and downstream sections; a plurality of feed injectornozzles circling the conduit and fixed with respect to the band toprovide feed injector tips that extend from an inside wall of theconduit and from the nozzle, all parts of the feed injector nozzlesremaining outside the inside diameter of the conduit, the injector tipoccupying at least half of a length of the band; and a fluid outletdefined by the downstream end of the conduit.